I managed to find a few examples for this, but I dont think they were exactly what I needed.
To make things worse I am a bit confused now as to which part of the circle starts at 0 radians. (Pretty sure its the east/right hand side rather than the north/top side of the circle).
Anyway, if you can imagine a point centered on the right-hand side of the circle, then moving clockwise from that point we will reach another given point on the circle. This is the angle (in radians) that I am after.
So, given a single point, a radius, and an origin(although I dont think the origin matters) we want to find the angle between the right-hand point (at 0 radians) and the given single point which can be anywhere on the circle.
I thought that I could do this with some trignometry and triangles, but then I realised anything over pi radians changes the direction of the triangle. I am looking for the clockwise angle between these two points, and I am pretty sure theres an equation for this, just havnt found one yet.
Given the Point P, the Radius R, and Origin O. Find the clockwise angle between the righthand point X and the point P.
This is something I cant answer, but hopefully someone here can! Thanks :o)